洛谷 P2370 P2370 yyy2015c01的U盘

https://www.luogu.org/problemnew/show/P2370

 

二分+背包

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <ctime>
using namespace std;
#define LL long long
#define mod int(1e9+7)
struct ahah
{
    int moon,val;
} a[1006];
bool cmp(ahah a,ahah b)
{
    return a.moon<b.moon;
}
int n,dp[1006],s,p;
bool check(int x)
{
    memset(dp,0,sizeof(dp));
    for(int i=1; i<=n; i++)
    {
        if(a[i].moon>x)break;
        for(int j=s; j>=a[i].moon; j--)
        {
            dp[j]=max(dp[j],dp[j-a[i].moon]+a[i].val);
        }
    }
//    cout<<x<<"\n";
//    for(int i=1;i<=n;i++)cout<<dp[i]<<" ";cout<<"\n";
    if(dp[s]>=p)return 1;
    else return 0;
}
int main()
{
    scanf("%d%d%d",&n,&p,&s);
    for(int i=1; i<=n; i++)scanf("%d%d",&a[i].moon,&a[i].val);
    sort(a+1,a+1+n,cmp);
    int l=1,r=n,ans=-1;
    while(l<=r)
    {
        int mid=(l+r)/2;
        if(check(a[mid].moon))
        {
            r=mid-1;
            ans=a[mid].moon;
        }
        else l=mid+1;
    }
    if(ans==-1)printf("No Solution!");
    else printf("%d",ans);
}